Generator shuts down

[inky]

I have a 1991 Onan Emerald III 6.3 propane generator. It has been running great. Ran it yesterday for about 5 hours and this morning for about a hour and a half. Went to start it this evening and starts great. The instant I let good of the start button it shuts down. It has plenty of oil, oil switch was changed out about 6 months ago, propand tank is more than half full. Nothing has changed since this morning when it ran great. We did drive through some horrible rain storms most of the day. However, the generator appears to be very dry. All other appliances are working fine on propane. Looking for any ideas what I can trouble shoot.

Thanks.

Joe

[inky]

Thanks for all the suggestions so far. To answer a few questions, The slip rings were cleaned in December. The problem I had last July turned out to be a faulty oil switch which was replaced. I have replaced a lot of parts on this generator. I am leaning towards maybe a low voltage problem. The regulator was replaced about 1000 running hours ago. The generator does not sit idle much at all. We use the generator all the time.

[Chris_Bryant]

I highly recommend buying and using the slick stick from Flight Systems to clean the slip rings if you have not- this is a common issue on these gensets. The resistance between the brushes and slip rings gets high, reducing the voltage fed to the rotor, reducing the output voltage. This makes the voltage regulator boost the voltage to the rotor. Normal voltage to the rotor should be around 18 volts. With tarnished slip rings, that voltage can get up to ~80 volts, whch the VR doesn't like to supply, and at which point the output voltage drops. Once it drops below ~90 volts, the genset will not run.
The slick stick is the easiest way to clean them.

[SaltiDawg]

What was the cause when you posted essentially the identical problem with your generator seven months ago?

Essentially The Same Post

[inky]

I just replaced the control board about 45 days ago and the oil switch about 90 days ago. I also replace the regulator about 2 years ago. I will check voltage in the morning as soon as all this rain stops.

Joe

[Chris_Bryant]

Try looking at the troubleshooting guide from Flight Systems- https://www.flightsystems.com/pdf/onan-rv-troubleshooing-guide.pdf- a very good guide.

[SaltiDawg]

I'd suggest looking at the oil sensor.

[ksg5000]

In general the Generator goes through a start up procedure which test whether their is sufficient oil and whether the generator is producing electricity - if either fails then the Generator shuts off.

You can rule out the oil sensor by bridging the contacts - if the generator runs fine after doing that replace the sensor. If it's not the sensor then it gets more complicated - might be brushes, regulator, circuit board etc.

The service manual on your generator s/b available on-line - it should outline how to test each of the possible causes for your problem. You might find a PDF for free or you can order one.

[Bionic_Man]

When my Honda did that a few years back it was because of a blown fuse.